
//获取滚动条当前的位置 
function getScrollTop() {
	var scrollTop = 0;
	if(document.documentElement && document.documentElement.scrollTop) {
		scrollTop = document.documentElement.scrollTop;
	} else if(document.body) {
		scrollTop = document.body.scrollTop;
	}
	return scrollTop;
}

//获取当前可视范围的高度 
function getClientHeight() {
	var clientHeight = 0;
	if(document.body.clientHeight && document.documentElement.clientHeight) {
		clientHeight = Math.min(document.body.clientHeight, document.documentElement.clientHeight);
	} else {
		clientHeight = Math.max(document.body.clientHeight, document.documentElement.clientHeight);
	}
	return clientHeight;
}

//获取文档完整的高度 
function getScrollHeight() {
	return Math.max(document.body.scrollHeight, document.documentElement.scrollHeight);
}